package com.example.demo.jwt;

import java.io.IOException;
import java.net.URLEncoder;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.shiro.authz.UnauthorizedException;
import org.apache.shiro.web.filter.authc.BasicHttpAuthenticationFilter;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.RequestMethod;

/**
 * shiro的http验证器
 * 
 * @author Administrator
 *
 */
public class JwtFilter extends BasicHttpAuthenticationFilter {

	/**
	 * 判断用户是否想要登入。 检测 header 里面是否包含 Token 字段
	 */
	@Override
	protected boolean isLoginAttempt(ServletRequest request, ServletResponse response) {
		HttpServletRequest req = (HttpServletRequest) request;
		String token = req.getHeader("Token");
		return token != null;
	}

	/**
	 * 如果带有 token，则对 token 进行检查，否则直接通过
	 * 在这里可以配置redis，判断用户是否是登陆
	 */
	@Override
	protected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue)
			throws UnauthorizedException {
		// 判断请求的请求头是否带上 "Token"
		if (isLoginAttempt(request, response)) {
			// 如果存在，则进入 executeLogin 方法执行登入，检查 token 是否正确
			try {
				executeLogin(request, response);
				return true;
			} catch (Exception e) {
				// token 错误
				responseError(response, e.getMessage());
			}
		}
		// 如果请求头不存在 Token，则可能是执行登陆操作或者是游客状态访问，无需检查 token，直接返回 true
		return true;
	}

	/**
	 * 执行登陆操作
	 */
	@Override
	protected boolean executeLogin(ServletRequest request, ServletResponse response) throws Exception {
		HttpServletRequest httpServletRequest = (HttpServletRequest) request;
		String token = httpServletRequest.getHeader("Token");
		JwtToken jwtToken = new JwtToken(token);
		// 提交给realm进行登入，如果错误他会抛出异常并被捕获
		getSubject(request, response).login(jwtToken);
		// 如果没有抛出异常则代表登入成功，返回true
		return true;
	}

	/**
	 * 将非法请求跳转到 /unauthorized/**
	 */
	private void responseError(ServletResponse response, String message) {
		try {
			HttpServletResponse httpServletResponse = (HttpServletResponse) response;
			// 设置编码，否则中文字符在重定向时会变为空字符串
			message = URLEncoder.encode(message, "UTF-8");
			httpServletResponse.sendRedirect("/unauthorized/" + message);
		} catch (IOException e) {
			System.out.println(e.getMessage());
		}
	}

	/**
	 * 对跨域提供支持
	 */
	@Override
	protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {
		HttpServletRequest httpServletRequest = (HttpServletRequest) request;
		HttpServletResponse httpServletResponse = (HttpServletResponse) response;
		httpServletResponse.setHeader("Access-control-Allow-Origin", httpServletRequest.getHeader("Origin"));
		httpServletResponse.setHeader("Access-Control-Allow-Methods", "GET,POST,OPTIONS,PUT,DELETE");
		httpServletResponse.setHeader("Access-Control-Allow-Headers",
				httpServletRequest.getHeader("Access-Control-Request-Headers"));
		// 跨域时会首先发送一个option请求，这里我们给option请求直接返回正常状态
		if (httpServletRequest.getMethod().equals(RequestMethod.OPTIONS.name())) {
			httpServletResponse.setStatus(HttpStatus.OK.value());
			return false;
		}
		return super.preHandle(request, response);
	}
}
